Carbon prepared by controlled pyrolysis of vinylidene chloride polymers (Saran carbon) has been described rather extensively in the literature, e.g., see the article by Ainscough, A. N., Dollimore, D., and Heal, G. R., "The Adsorption Characteristics of Polyvinylidene Chloride Carbon", Carbon 11, 189-197 (1973); and "Thermodynamics of Polyvinylidene Chloride in the Solid State" by Wessling, R. A. and Bohme, R. D. in Journal of Applied Polymer Science, Vol. 16, pp 1761-1778 (1972).
The kinetics of the dehydrochlorination reaction have also been discussed, e.g., by: Dacey, J. R., and Cadenhead, D. A. (The Royal Military College of Canada, Kingston, Ontario), "The Formation of Carbon from Polyvinylidene Chloride", Proceedings of the Fourth Conference on Carbon, Pergammon Press, N.Y. (1960), pp. 315-319; Everett, D. H., Redman, E., and (in part) Miles, A. J., and Davies, D. H. (The University, Bristol), "Saran Charcoals: Some Observations of Their Preparation and Adsorptive Properties", Fuel 42, 219-228 (1963); Fredler, A., and Fitzer, E. (Universitat Karlsruhe), "Kinetics for the Pyrolysis of Polyvinylidene Chloride", 3rd Conf. on Ind. Carbons and Graphite, 131-135 (1970) (London: Soc. of Chem. Ind.); and Burnett, G. M., Haldon, R. A. (The Univ. Aberdeen), and Hay, J. N. (The Univ., Birmingham), "Dehydrochlorination of Polymers - I. Polyvinylidene Chloride", Eur. Polymer J. 3, 449-457 (1967).
The morphology of carbon prepared from vinylidene chloride polymers has been discussed by: Bailey, A., and Everett, D. H. (U. of Bristol), "New Evidence for the Fine Structure of Porous Carbons", Nature 211, 1082-1083 (1966); Bailey, A., and Everett, D. H. (University of Bristol), "Morphology of Poly(vinylidene chloride) and of Carbons Resulting from its Pyrolysis", Journal of Polymer Science, A-2, 7, 87-104 (1969); Adams, L. B., Boucher, E. A., Cooper, R. N., and Everett, D. H. (U. of Bristol) "Preparation, Structure and Properties of Saran Carbon Fibres and Powders", 3rd Conf. on Ind. Carbons and Graphite, 478-482 (1970) (London: Soc. of Chem. Ind.); Boult, E. H., Campbell, H. G., and Marsh, H. (U. of Newcastle-upon-Tyne), "The Carbonization of Polyvinylidene Chloride -- an Investigation using Scanning Electron Microscopy", Carbon 7, 700-701 (1969); and Franklin, Rosaline E., "Crystallite Growth in Graphitizing and Nongraphitizing Carbons", Royal Soc. London Proc. 209A, 196-218 (1951).
The molecular sieve properties of vinylidene chloride polymers, i.e., the ability of carbonized vinylidene chloride polymers to adsorb small molecules but not relatively large molecules, has also been discussed. The sizes of the micropores have been described to be from about 5 to 12 A in diameter, depending on polymer composition and heat treatment temperatures. Pertinent references include: Lamond T. G., Metcalf, J. E., III, and Walker, P. L., Jr. (Penn State), "6 A Molecular Sieve Properties of Saran-Type Carbons", Carbon 3, 59-63, (1965); Walker, P. L., Jr. (Penn State U., University Park, Pa.), "Molecular Sieves", Mineral Industries, Penn State Univ. 35 (4), 1-7 (1966); Dacey, J. R., and Thomas, D. G. (Royal Military College of Canada, Kingston, Ontario), "Adsorption on Saran Charcoal", Trans. Faraday Soc. 50, 740-748 (1954); and Barton, Stuart S., Boulton, Gordon L., Dacey, J. R., Evans, M. J. B., and Harrison, Brian H. (Royal Military College), "Heat of Immersion Studies on Carbon Formed from Polyvinylidene Chloride", J. Colloid Interface Sci. 44, 50-56 (1973 ).
Some workers have increased pore sizes of such carbons by post-activation of the carbon with carbon dioxide or water at elevated temperature, e.g., see the following articles: Walter, P. L., Jr., Lamond, T. G., and Metcalf, J. E., III (Penn State U.), "The Preparation of 4A and 5A Carbon Molecular Sieves", 2nd Conf. Ind. Carbon and Graphite, pp. 7-14, 1966 (London: Soc. Chem. Ind.); Culver, R. V., and Heath, N. S. (U. of Adelaide, South Australia), "Saran Charcoals. Part 1 - Activation and Adsorption Studies", Trans. Faraday Soc. 51, 1569-1575 (1955); Marsh, H., and Campbell, H. G., (U. of Newcastle upon Tyne), "The Characteristics of Microporous Carbons by Adsorption from Liquid and Vapor Phases", Carbon 9, 489-498 (1971); Lamond, T. G., and Marsh, H. (Newcastle upon Tyne), "The Surface Properties of Carbon. III -- The Process of Activation of Carbons", Carbon 1, 293-307 (1964); and Siedlewski, Janusz, and Rychlicki, Gerald (Copernicus Univ. Forun, Poland), "Investigation of the carbon sorbents made from organic polymers. I. The porous structure and the adsorptive capacities of the Saran carbons activated by carbon dioxide and water vapor", Chemia Stosowana XV, 369-382 (1971).
Other literature describes dehydrochlorination of vinylidene chloride polymers with bases to produce carbon. Pertinent references are: Evans, Brian, and Flood, E. A. (National Research Council of Canada, Ottawa), "Low Temperature Carbonization of Polyvinylidene Chloride", Can. J. Chem. 45, 1713-1714 (1967); Evans, Brian, and Flood, Edward A. (assignors to Canadian Patents and Development Limited, Ottawa), "Microporous Carbon Preparation", U.S. Pat. No. 3,516,791, Patented June 23, 1970; and Barton, Stuart S., Boulton, Gordon, Harrison, B. H., and Kemp, William (Royal Military College of Canada), "Study of the Dehydrochlorination of Polyvinylidene Chloride by Alcholic Base, Using Ultra-Violet Adsorption Spectroscopy", Trans. Faraday Society 67, 3534-3539 (1971).
The following uses for carbonized vinylidene chloride polymers have also been disclosed: Badishe Arilin- & Soda Fabrik Aktiengesellschaft, "Chromatographic Separating Process and/or Analysis of Mixtures of Materials", Netherland Pat. No. 7,010,263, July 10, 1970; Kaiser, R. (Badishe Arilin- & Soda Fabrik AG), "Kohlenstoff-Molekularsieb", Chromatographia 3, 38-40 (1970); Zlatkis, A., Kaufman, H. R., and Durbin, D. E. (University of Houston), "Carbon Molecular Sieve Columns for Trace Analysis in Gas Chromatography", Journal of Chromotographic Science 8, 416-417 (1970); Lamond and Marsh, Carbon, Vol. 1, pp. 293-307 (1964), which article discloses adsorbing ethyl chloride on carbon to determine the surface area of such carbon; Rippberger, Willi, Oettinger, Willi, Kaiser, Rudolf, Pfitzner, Klaus, and Palm, Richard Adolf (BASF) "Manufacturing of Carbon by Cleavage of Hydrogen Halide from Polymeric Halogenated Hydrocarbons", German Pat. No. 2,104,657, Feb. 2, 1971; Reed, Madison W., Jr., and Schwemer, Warren C. (Advanced Technology Center, Inc., Arlington, Texas), "Method of Making a Porous Carbon Material", U.S. Pat. No. 3,647,551, Mar. 7, 1972; Reed, M. W., and Schwemer, W. C. (LTV Research Center, Dallas), "Porous Carbon Fuel Cell Electrodes from Polymer Precursors", J. Electrochem. Soc. 114, 582-585 (1967); and Mahajan, O. P., Walker, P. L., Jr. (Penn State), "Krypton Adsorption on Microporous Carbons and 5A Zeolite", J. Coll. Interface Sci. 29, 129-137 (1969).
Heretofore, however, it has been the practice in conducting quantitative analysis determinations, to adsorb the molecules to be analyzed on an activated carbon followed by desorption and analysis of the desorbed material. Exemplary of such prior knowledge is the disclosure in the article entitled "A Convenient Optimized Method for the Analysis of Selected Solvent Vapors in the Industrial Atmosphere" by White et al in American Industrial Hygiene Association, J. 31, 225-232 (1970). Conventionally used commercially available activated carbons, and particularly those derived from vegetable origins, e.g., coal and coconut shells, vary widely in composition. For example, the article entitled "Active Carbon" by Smisek and Cerny, Elsevier, New York, Page 62 (1970), discloses that an active carbon prepared from coconut shells contained 3.5 percent ash, including significant amounts, i.e., tenths of a percent, of potassium, aluminum, silicon, sodium and iron oxides and somewhat lesser amounts of magnesium, calcium, boron, copper, zinc and tin as well as trace amounts of lithium, rubidium, strontium and lead. The presence of these impurities prevents analytical determinations of substances while adsorbed on such carbons. Further, prior used active carbons are relatively soft resulting in carbon dusting and additional analytical uncertainty.
It is a primary object of the present invention to provide a means for quantitatively analyzing substances containing elements other than carbon, hydrogen and oxygen by adsorbing such substances on a carbonized material which is substantially dust and contaminant free and wherein such substances can be analyzed while still adsorbed on the carbon surface or, if desired, effectively desorbed for purposes of highly accurate analysis.
A further object is to provide an effective means for adsorbing relatively large amounts of highly volatile toxic vapors such as vinyl chloride or vinylidene chloride on a substantially dust and contaminant free carbon material, e.g., wherein such carbon is contained in an air-sampling tube as conventionally used to measure the concentrations of such materials in industrial locations.